Portable refrigerators small enough to carry in a pocket have been suggested for cooling small quantities of material such as insulin and allergy medicine that must be kept at cool temperatures for proper preservation. Such small scale refrigerators have used a small container of a pressurized liquid that can be vaporized into the cooling chamber, but regulating the temperature in a simple and reliable way and extending the cooling capacity for a practical length of time with a small quantity of coolant has not been achieved.
On a larger scale, portable refrigerators for recreational uses such as camping, boating, and travel can also be cooled effectively by vapor escaping from a container of pressurized liquid, so long as a simple thermostat system can regulate the cooling temperature. This can avoid the bother of melting ice that is usually used for portable refrigerators.
This invention involves recognition of the problems of vapor-cooled portable refrigerators and proposes a regulating system that is simple, compact, and reliable and attains a lengthy cooling period from a small supply of coolant. The invention aims at low cost, convenience, long-range capacity, and reliable operation for a thermal regulating system for a small portable refrigerator.